Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond readOnlyHint/openWorldHint, it discloses the data source (JSON embedded in the public page), absence of authentication, the cost model ($0.002 USDC per successful call via x402 on Base/Solana/Arc), and crucially that failed calls are not charged. It also explicitly discloses a negative capability (no live altitude/speed), which annotations cannot convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Returned fields and scope are front-loaded, followed by access method, limitations, and pricing in a logical order. Slightly dense as a single block, but every sentence carries information an agent needs.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present, return values need no explanation, and the description covers source, auth, cost, and limitations. The one gap is temporal: with only an ident and no date, it doesn't say how a recurring daily flight number is resolved (current/next flight), which matters for a public tracker.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and the single parameter already documents the UAL956-style format with a length constraint. The description's phrase 'for one flight number' corroborates the schema but adds no syntax, casing, or format detail beyond it, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific resource (public FlightAware page) and a specific retrieval (by flight number), then enumerates exactly what is returned: airline, aircraft type, origin/destination with IATA codes, status, and the ident. That field enumeration makes it clearly distinguishable from siblings like flightradar24_live_flights or google_flights.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives a clear condition of use ('one flight number', 'no login') and an explicit exclusion — 'Live altitude and speed are not included on the page used' — which steers an agent away from this tool when live positional data is required. It stops short of naming the alternative sibling to use instead, so it is not a full 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.